For certain applications it is necessary to determine the position of a point source of radiant energy from a location remote from the source. In one application, it is necessary to determine the position of terrestrial radio frequency energy, as emitted from a microwave relay tower, that interferes with a communication link including a relay station on a geostationary, synchronous satellite. The frequencies of the satellite communication link and the energy emitted from the tower are in the same portion of the spectrum so that the latter is considered to interfere with the former. Before the effect of such interference can be determined, the existence and position of the source must be determined. To the satellite relay, the tower emission is sufficiently distant to appear as a point source.
Perhaps, the most straightforward method of determining the position of an interfering source with a satellite communication link is to determine the field pattern of each possible emitter in the frequency range of the communication link. Such a procedure is undesirable for several reasons, amongst which are the costs in identifying each of the possible emitters and determining the field pattern and intensity of side lobes of the sources. In addition, such a method is inherently inaccurate because of spurious signals that could be coupled from the interfering source into the communication link.
Another possible technique for determining the position of an interfering source involves spot pointing the beam of a narrow beam antenna on the spacecraft at many different adjacent areas, which together cover a region which is desired to investigate. Such a procedure is both time consuming and expensive.
The present invention is described in particular with regard to determining the position of an interfering source of radio frequency energy, e.g., a terrestrial microwave relay tower, with a communication link including a geostationary, synchronous satellite that includes a relay station of the link. It is to be understood however, that many of the principles are equally applicable to determining the position of any point source of radiant energy from a location remote from the source, ragardless of whether the electromagnetic energy source is in the RF infrared, visible light, or ultraviolet frequency spectrum; further the invention is applicable to point sources of acoustic energy.
It is, accordingly, an object of the present invention to provide a new and improved method and apparatus for determining the position of a point source of radiant energy from a location remote from the source.
Another object of the invention is to provide a new and improved apparatus for and method of determining the position of a point source of radiant energy without investigating and plotting the pattern of all possible sources of such radiation in a region of interest.
Another object of the invention is to provide a new and improved apparatus for and method of determining the position of interfering, terrestrial radio frequency sources with communication links including a relay station mounted on a geostationary, synchronous satellite.